Lavender essential oil sustained-release capsule for air purification and preparation method of lavender essential oil sustained-release capsule

Abstract

The invention discloses a lavender essential oil sustained-release capsule for air purification and a preparation method of the lavender essential oil sustained-release capsule, relates to the field of microcapsules, and aims to solve the problems that existing lavender essential oil is easy to volatilize quickly and poor in function synergy when being used for air purification. The preparation method comprises the following steps: firstly, preparing modified mesoporous silica and modified bamboo charcoal powder, wherein the modified mesoporous silica is prepared by vinyl modification, hydrophobic grafting and epoxy introduction; the modified bamboo charcoal powder is prepared by activation, oxidation and polyethyleneimine grafting. And combining lavender essential oil with the modified mesoporous silica to form an essential oil-mesoporous compound, preparing chitosan and the modified bamboo charcoal powder into a bamboo charcoal composite solution, mixing the essential oil-mesoporous compound and the bamboo charcoal composite solution, adding glutaraldehyde for crosslinking, and drying to obtain the sustained-release capsule. The capsule prepared by the invention can realize long-term stable slow release of essential oil and high-efficiency degradation of harmful gases such as formaldehyde, the process is environment-friendly and controllable, large-scale production is easy, and the capsule is suitable for indoor air purification scenes such as families and offices.

Description

Technical Field

[0001] This invention relates to the field of microcapsules, specifically to a lavender essential oil sustained-release capsule for air purification and its preparation method. Background Technology

[0002] In the field of using lavender essential oil for air purification, one of the core pain points is the poor encapsulation and slow-release effect of the essential oil. Existing technologies mostly use unmodified mesoporous materials, ordinary resins, or natural polymers as carriers. These carriers either have weak adsorption capacity for essential oils or lack effective hydrophobic locking structures, causing the essential oils to easily evaporate and leak during storage and use. This not only shortens the duration of the aroma and purification functions but also wastes the essential oil raw materials, making it difficult to meet the needs of long-term stable air purification.

[0003] Existing products that combine essential oil slow-release and harmful gas purification functions generally suffer from poor functional synergy. Some products only focus on the aroma and basic antibacterial effects of essential oils, without designing efficient adsorption and purification structures for major indoor harmful gases such as formaldehyde. Even when adsorption materials such as bamboo charcoal are added, they are mostly unmodified raw bamboo charcoal, which has a limited specific surface area and few surface active groups, resulting in low adsorption capacity for formaldehyde and difficulty in achieving chemical fixation. This leads to short-lived purification effects that are easily saturated, failing to simultaneously meet the dual requirements of stable essential oil release and efficient purification of harmful gases.

[0004] At the manufacturing process level, existing technologies lack systematic modification design for carrier materials. For example, mesoporous materials often undergo only a single-step surface modification, failing to simultaneously achieve high essential oil loading, strong locking, and cross-linking with the carrier; bamboo charcoal materials also often omit key steps such as activation, oxidation, or functional grafting, making it difficult to form a stable composite network structure with other carriers. This simplified process results in a loose final product structure, leading to essential oil leakage due to weak inter-carrier bonding and reduced purification efficiency due to insufficient adsorption material activity, thus failing to achieve comprehensive performance optimization. Therefore, given the limitations of the aforementioned technologies, there is an urgent need to develop a lavender essential oil sustained-release capsule for air purification and its preparation method. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a lavender essential oil sustained-release capsule for air purification and its preparation method, which effectively solves the problems of rapid volatilization, short duration of action, and frequent replenishment of existing lavender essential oils used for air purification.

[0006] The objective of this invention can be achieved through the following technical solutions: On one hand, the present invention provides a method for preparing lavender essential oil sustained-release capsules for air purification, comprising the following preparation steps: S1: Add lavender essential oil to anhydrous ethanol to obtain a lavender essential oil ethanol solution. Add modified mesoporous silica to the lavender essential oil ethanol solution and disperse it by ultrasonication. Let it stand and separate by centrifugation to obtain an essential oil-mesoporous complex. S2: Add chitosan to acetic acid solution and stir evenly, add modified bamboo charcoal powder, and ultrasonically disperse to obtain bamboo charcoal composite solution; S3: Add the essential oil-mesoporous complex to the bamboo charcoal composite solution, stir and disperse to obtain a suspension, add the cross-linking agent solution to the suspension, heat and stir after the cross-linking agent solution is added, filter, wash and dry to obtain lavender essential oil sustained-release capsules for air purification.

[0007] Further, in step S1, the modified mesoporous silica is prepared by the following method: A1: Mesoporous silica was added to toluene, followed by vinyltrimethoxysilane. The pH was adjusted, and the mixture was stirred under reflux under nitrogen protection. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain vinyl-modified mesoporous silica. A2: Vinyl-modified mesoporous silica was added to xylene, followed by dodecyl methacrylate and azobisisobutyronitrile. After ultrasonic dispersion, the mixture was heated and stirred under nitrogen protection. After the reaction was completed, petroleum ether was added, the mixture was allowed to stand, and then centrifuged to obtain grafted mesoporous silica. A3: Grafted mesoporous silica was added to isopropanol, followed by epichlorohydrin and triethylamine. The mixture was heated and stirred to react. After the reaction was completed, the silica was centrifuged, washed, and dried to obtain modified mesoporous silica.

[0008] Further, in step A1, the pH is adjusted to 4.0-5.0, the reflux stirring reaction temperature is 70℃-80℃, the reaction time is 4h-6h, the centrifugation speed is 3500rpm-4500rpm, the centrifugation time is 12min-18min, the drying temperature is 60℃-80℃, and the drying time is 4h-6h.

[0009] Further, in step A2, the ultrasonic dispersion power is 300W-500W, and the ultrasonic time is 15min-25min; the reaction temperature for heating and stirring is 65℃-75℃, and the reaction time is 8h-12h; the amount of petroleum ether added is 2-3 times the mass of xylene, the standing time is 4h-6h, the centrifugation speed is 4000rpm-5000rpm, and the centrifugation time is 15min-20min.

[0010] Further, in step A3, the reaction temperature for heating and stirring is 50℃-60℃, and the reaction time is 5-7h; the centrifugation speed is 4500rpm-5500rpm, and the time is 18min-25min; during washing, the mixture is first washed 1-2 times with a 5% sodium bicarbonate solution, and then washed 2-3 times with deionized water; the drying is carried out in stages, first drying at 60℃-70℃ for 3h-4h, and then drying at 80℃-85℃ for 2h-3h.

[0011] Furthermore, the raw materials for the modified mesoporous silica, by weight, include: 70-100 parts mesoporous silica, 800-1200 parts toluene, 15-25 parts vinyltrimethoxysilane, 1500-2000 parts xylene, 200-300 parts dodecyl methacrylate, 3-6 parts azobisisobutyronitrile, 800-1200 parts isopropanol, 50-80 parts epichlorohydrin, and 10-15 parts triethylamine.

[0012] Further, in step S2, the modified bamboo charcoal powder is prepared by the following method: B1: Take bamboo charcoal powder, sieve it, add potassium hydroxide solution, stir and activate it, cool it, filter it and dry it; then place it in a tube furnace, heat and keep it in a nitrogen atmosphere, and after natural cooling, obtain highly active bamboo charcoal powder. B2: Add highly active bamboo charcoal powder to potassium permanganate solution and stir to react. Add hydrochloric acid solution and continue stirring. Filter and dry to obtain oxidized bamboo charcoal powder. B3: Add oxidized bamboo charcoal powder to an aqueous solution of polyethyleneimine and disperse it by ultrasonication. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to react. After the reaction, collect the solid by centrifugation, wash and dry to obtain modified bamboo charcoal powder.

[0013] Further, in step B1, the bamboo charcoal is pulverized and passed through a 200-300 mesh sieve; the stirring activation temperature is 75℃-85℃, and the activation time is 3h-5h; the drying temperature is 105℃-115℃, and the drying time is 4h-6h; the heating rate of the tube furnace is 4℃ / min-6℃ / min, and after heating to 780℃-820℃, it is kept at that temperature for 1.5h-2.5h.

[0014] Furthermore, in step B2, the stirring reaction temperature is 25℃-35℃, the reaction time is 2.5h-3.5h, the stirring time is 30min-45min, and the drying is vacuum drying with a drying temperature of 55℃-65℃, a vacuum degree of -0.08MPa-0.1MPa, and a drying time of 3.5h-4.5h.

[0015] Further, in step B3, the ultrasonic dispersion power is 280W-320W, the dispersion time is 12min-18min, the stirring reaction temperature is 32℃-38℃, the reaction time is 5.5-6.5, the centrifugation speed is 3800rpm-4200rpm, and the centrifugation time is 12min-18min; the washing process involves washing with deionized water 3-4 times, and the drying is carried out by vacuum drying at a temperature of 65℃-75℃ for 4.5h-5.5h.

[0016] Furthermore, the raw materials for the modified bamboo charcoal powder, by weight, include: 12-20 parts bamboo charcoal, 110-170 parts potassium hydroxide solution, 80-100 parts potassium permanganate solution, 30-50 parts hydrochloric acid solution, 70-90 parts polyethyleneimine aqueous solution, and 8-11 parts 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

[0017] Furthermore, the molecular weight of the polyethyleneimine is 30,000.

[0018] Further, the potassium hydroxide solution has a mass fraction of 8%-12%, the potassium permanganate solution has a mass fraction of 4%-6%, the hydrochloric acid solution has a mass concentration of 0.08mol / L-0.12mol / L, and the polyethyleneimine aqueous solution has a mass fraction of 7%-9%.

[0019] Further, in step S1, the mass ratio of lavender essential oil to anhydrous ethanol is 1:2.3-3.7, and the mass ratio of modified mesoporous silica to lavender essential oil ethanol solution is 1:5.5-9.5; the ultrasonic dispersion power is 400W-500W, and the time is 40min-50min; the standing temperature is 28℃-32℃, and the standing time is 5h-7h; the centrifugation speed is 7000rpm-9000rpm, and the centrifugation time is 10min-15min.

[0020] Further, in step S2, the mass ratio of chitosan to acetic acid solution is 1:40-50, the mass fraction of acetic acid solution is 0.8%-1.2%, the mass ratio of modified bamboo charcoal powder to chitosan is 1:4-1:5; the ultrasonic dispersion power is 350W-450W, and the time is 20min-30min.

[0021] Further, in step S3, the mass ratio of the essential oil-mesoporous complex to the bamboo charcoal composite solution is 1:8.5-11.5; the stirring and dispersion speed is 350rpm-450rpm, and the time is 25min-35min; the crosslinking agent solution is a glutaraldehyde aqueous solution with a mass fraction of 1.5%-2.5%, and the mass ratio of the suspension to the crosslinking agent solution is 1:3.8-4.8; the temperature for heating and stirring is 40℃-45℃, the stirring speed is 250rpm-300rpm, and the time is 2h-2.5h.

[0022] On the other hand, the present invention provides a lavender essential oil sustained-release capsule for air purification, which is prepared by the above-described preparation method.

[0023] The beneficial effects of this invention are: 1. This invention utilizes a composite carrier structure of "modified mesoporous silica-modified bamboo charcoal powder-chitosan," combined with vinyl modification, hydrophobic grafting, and epoxy introduction of mesoporous silica, along with activation, oxidation, and polyethyleneimine grafting of bamboo charcoal powder. This effectively locks in lavender essential oil, significantly reducing leakage during storage and use, achieving long-term stable and sustained release of the essential oil, and continuously exerting its aroma-regulating and air-purifying effects without the need for frequent replenishment or replacement.

[0024] 2. After gradient activation, oxidation and polyethyleneimine grafting, modified bamboo charcoal powder can efficiently adsorb harmful gases such as formaldehyde in the air. At the same time, with the synergistic effect of modified mesoporous silica and chitosan, it can further enhance the adsorption-degradation effect of harmful gases, significantly improve indoor air quality, and the purification effect is long-lasting and not easily ineffective due to adsorption saturation.

[0025] 3. In the preparation process of this invention, the carrier materials such as mesoporous silica, bamboo charcoal powder, and chitosan used are widely available and environmentally friendly, with no risk of harmful residues; the parameters of each modification step and composite preparation process are clear and controllable, facilitating large-scale industrial production. The product is suitable for various indoor scenarios such as homes, offices, and vehicles, achieving air purification and fragrance regulation while also possessing good safety and practicality. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this embodiment of the invention, the molecular weight of the polyethyleneimine is 30,000, and it was purchased from Shanghai Lulun New Material Technology Co., Ltd.

[0028] In this embodiment of the invention, the mesoporous silica particles with a size of 0.002 mm were purchased from Auscatalytic Materials (Dalian) Co., Ltd.

[0029] Example 1 A method for preparing lavender essential oil sustained-release capsules for air purification includes the following preparation steps: A1: 70 parts of mesoporous silica with a particle size of 0.002 mm were added to 800 parts of toluene, followed by 15 parts of vinyltrimethoxysilane. The pH of the system was adjusted to 4.0 with 10% (w / w) dilute acetic acid. Nitrogen gas was introduced for protection and maintained at a flow rate of 0.8 L / min. The mixture was refluxed and stirred at 70 °C for 4 h. After the reaction was completed, the solid was collected by centrifugation at 3500 rpm for 12 min. The solid was washed three times with toluene and twice with anhydrous ethanol, and then dried in a 60 °C drying oven for 4 h to obtain vinyl-modified mesoporous silica. A2: All the vinyl-modified mesoporous silica obtained in A1 was added to 1500 parts xylene, followed by 200 parts dodecyl methacrylate and 3 parts azobisisobutyronitrile. The mixture was ultrasonically dispersed at 300W for 15 min, then heated to 65℃ under nitrogen protection and stirred at a constant temperature for 8 h. After the reaction was completed, 3000 parts petroleum ether was added to the system, and the mixture was allowed to stand for 4 h to allow the solid to fully separate. The solid was then collected by centrifugation at 4000 rpm for 15 min to obtain grafted mesoporous silica. A3: All the grafted mesoporous silica obtained in A2 was added to 800 parts of isopropanol, followed by 50 parts of epichlorohydrin and 10 parts of triethylamine. The mixture was heated to 50°C and stirred at a constant temperature for 5 hours. After the reaction was completed, the solid was collected by centrifugation at 4500 rpm for 18 minutes. The solid was washed once with a 5% sodium bicarbonate solution and then twice with deionized water. It was then dried at 60°C for 3 hours and then heated to 80°C for 2 hours to obtain modified mesoporous silica. B1: Take 12 parts of bamboo charcoal, crush it and pass it through a 200-mesh sieve. Add 110 parts of 8% potassium hydroxide solution and stir to activate it at 75℃ for 3 hours. After activation, cool to room temperature, filter and collect the solid, wash it with deionized water until neutral, and dry it in a 105℃ drying oven for 4 hours. Put the dried solid into a tube furnace, purge it with nitrogen for protection, heat it to 780℃ at a rate of 4℃ / min, hold it at that temperature for 1.5 hours, and then cool it naturally to room temperature to obtain highly active bamboo charcoal powder. B2: Add all the highly active bamboo charcoal powder obtained in B1 to 80 parts of a 4% potassium permanganate solution and stir at 25°C for 2.5 h. After the reaction is complete, add 30 parts of a 0.08 mol / L hydrochloric acid solution to the system and continue stirring for 30 min. Then filter to collect the solid, wash with deionized water until neutral, place in a vacuum drying oven, and dry at 55°C and -0.08 MPa for 3.5 h to obtain oxidized bamboo charcoal powder. B3: All the oxidized bamboo charcoal powder obtained in B2 was added to 70 parts of a 7% (w / w) aqueous solution of polyethyleneimine (molecular weight of polyethyleneimine 30,000), and ultrasonically dispersed at 280W for 12 min. Then, 8 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide were added, and the mixture was stirred and reacted at 32℃ for 5.5 h. After the reaction was completed, the solid was collected by centrifugation at 3800 rpm for 12 min. The solid was washed three times with deionized water and then once with anhydrous ethanol. It was then placed in a vacuum drying oven and dried at 65℃ for 4.5 h to obtain modified bamboo charcoal powder. S1: Lavender essential oil and anhydrous ethanol were mixed at a mass ratio of 1:2.3. The lavender essential oil was added to the anhydrous ethanol and stirred until homogeneous to obtain a lavender essential oil ethanol solution. The modified mesoporous silica obtained in A3 was added to this solution at a mass ratio of 1:5.5 to the lavender essential oil ethanol solution. The mixture was ultrasonically dispersed at 400W for 40 min and then allowed to stand at 28℃ for 5 h. After standing, the solid was collected by centrifugation at 7000 rpm for 10 min to obtain the essential oil-mesoporous complex. S2: Add chitosan to a 0.8% acetic acid solution with a mass ratio of chitosan to acetic acid solution of 1:40. Stir until the chitosan is completely dissolved. Add the modified bamboo charcoal powder obtained in B3 to the solution with a mass ratio of modified bamboo charcoal powder to chitosan of 1:4. Disperse the solution with ultrasonic power at 350W for 20 minutes to obtain a bamboo charcoal composite solution. S3: The essential oil-mesoporous complex obtained in S1 was added to the bamboo charcoal composite solution obtained in S2, with a mass ratio of essential oil-mesoporous complex to bamboo charcoal composite solution of 1:8.5. The mixture was stirred and dispersed at 350 rpm for 25 min to obtain a suspension. A 1.5% (w / w) glutaraldehyde aqueous solution was added to the suspension, with a mass ratio of suspension to glutaraldehyde aqueous solution of 1:3.8. After all the solution was added, the temperature was raised to 40℃, and the mixture was stirred at a constant temperature of 250 rpm for 2 h. After the reaction was completed, the solid was collected by filtration, washed four times with deionized water, and then dried in a vacuum drying oven at 75℃ for 6 h to obtain lavender essential oil sustained-release capsules for air purification. Example 2 A method for preparing lavender essential oil sustained-release capsules for air purification includes the following preparation steps: A1: 85 parts of mesoporous silica with a particle size of 0.002 mm were added to 1000 parts of toluene, followed by 20 parts of vinyltrimethoxysilane. The pH of the system was adjusted to 4.5 with 10% (w / w) dilute acetic acid. Nitrogen gas was introduced for protection and maintained at a flow rate of 1.0 L / min. The mixture was refluxed and stirred at 75 °C for 5 h. After the reaction was completed, the solid was collected by centrifugation at 4000 rpm for 15 min. The solid was washed three times with toluene and twice with anhydrous ethanol, and then dried in a 70 °C drying oven for 5 h to obtain vinyl-modified mesoporous silica. A2: All the vinyl-modified mesoporous silica obtained in A1 was added to 1750 parts xylene, followed by 250 parts dodecyl methacrylate and 4.5 parts azobisisobutyronitrile. The mixture was ultrasonically dispersed at 400W for 20 min, then heated to 70℃ under nitrogen protection and stirred at a constant temperature for 10 h. After the reaction was completed, 4375 parts petroleum ether was added to the system, and the mixture was allowed to stand for 5 h to allow the solid to fully separate. The solid was then collected by centrifugation at 4500 rpm for 18 min to obtain grafted mesoporous silica. A3: All the grafted mesoporous silica obtained in A2 was added to 1000 parts of isopropanol, followed by 65 parts of epichlorohydrin and 12.5 parts of triethylamine. The mixture was heated to 55°C and stirred at a constant temperature for 6 hours. After the reaction was completed, the solid was collected by centrifugation at 5000 rpm for 22 minutes. It was washed once with a 5% sodium bicarbonate solution and then three times with deionized water. Subsequently, it was dried at 65°C for 4 hours and then heated to 82°C for 2.5 hours to obtain modified mesoporous silica.

[0030] B1: Take 16 parts of bamboo charcoal, crush it and pass it through a 250-mesh sieve. Add 140 parts of a 10% potassium hydroxide solution and stir to activate it at 80℃ for 4 hours. After activation, cool to room temperature, filter to collect the solid, wash it with deionized water until neutral, and dry it in a 110℃ drying oven for 5 hours. Place the dried solid in a tube furnace, purge it with nitrogen for protection, heat it to 800℃ at a rate of 5℃ / min, hold it at that temperature for 2 hours, and then cool it naturally to room temperature to obtain highly active bamboo charcoal powder. B2: Add all the highly active bamboo charcoal powder obtained in B1 to 90 parts of a 5% potassium permanganate solution and stir at 30°C for 3 hours. After the reaction is complete, add 40 parts of a 0.1 mol / L hydrochloric acid solution to the system and continue stirring for 38 minutes. Then filter to collect the solid, wash with deionized water until neutral, place in a vacuum drying oven, and dry at 60°C and -0.09 MPa for 4 hours to obtain oxidized bamboo charcoal powder. B3: All the oxidized bamboo charcoal powder obtained in B2 was added to 80 parts of 8% (w / w) polyethyleneimine aqueous solution (polyethyleneimine molecular weight 30,000), and ultrasonically dispersed at 300W for 15 min. Then, 9.5 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide were added, and the mixture was stirred and reacted at 35℃ for 6 h. After the reaction was completed, the solid was collected by centrifugation at 4000 rpm for 15 min. The solid was washed three times with deionized water and then once with anhydrous ethanol. It was then placed in a vacuum drying oven and dried at 70℃ for 5 h to obtain modified bamboo charcoal powder. S1: Lavender essential oil and anhydrous ethanol were mixed at a mass ratio of 1:3.0. The lavender essential oil was added to the anhydrous ethanol and stirred until homogeneous to obtain a lavender essential oil ethanol solution. The modified mesoporous silica obtained in A3 was added to this solution, with a mass ratio of modified mesoporous silica to lavender essential oil ethanol solution of 1:7.5. The mixture was ultrasonically dispersed at 450W for 45 min, and then allowed to stand at 30℃ for 6 h. After standing, the solid was collected by centrifugation at 8000 rpm for 12 min to obtain the essential oil-mesoporous complex.

[0031] S2: Add chitosan to a 1% (w / w) acetic acid solution, with a chitosan to acetic acid solution mass ratio of 1:45. Stir until the chitosan is completely dissolved. Add the modified bamboo charcoal powder obtained in B3 to the solution, with a modified bamboo charcoal powder to chitosan mass ratio of 1:4.5. Disperse the solution with ultrasonic power at 400W for 25 minutes to obtain a bamboo charcoal composite solution. S3: The essential oil-mesoporous complex obtained in S1 was added to the bamboo charcoal composite solution obtained in S2, with a mass ratio of essential oil-mesoporous complex to bamboo charcoal composite solution of 1:10. The mixture was stirred and dispersed at 400 rpm for 30 min to obtain a suspension. A 2% (w / w) glutaraldehyde aqueous solution was added to the suspension, with a mass ratio of suspension to glutaraldehyde aqueous solution of 1:4.3. After all the solution was added, the temperature was raised to 42℃, and the mixture was stirred at a constant temperature of 280 rpm for 2.2 h. After the reaction was complete, the solid was collected by filtration, washed four times with deionized water, and then dried in a vacuum drying oven at 75℃ for 6 h to obtain lavender essential oil sustained-release capsules for air purification.

[0032] Example 3 A method for preparing lavender essential oil sustained-release capsules for air purification includes the following preparation steps: A1: 100 parts of mesoporous silica with a particle size of 0.002 mm were added to 1200 parts of toluene, followed by 25 parts of vinyltrimethoxysilane. The pH of the system was adjusted to 5.0 with 10% (w / w) dilute acetic acid. Nitrogen gas was introduced for protection and maintained at a flow rate of 1.2 L / min. The mixture was refluxed and stirred at 80 °C for 6 h. After the reaction was completed, the solid was collected by centrifugation at 4500 rpm for 18 min. The solid was washed three times with toluene and twice with anhydrous ethanol, and then dried in an 80 °C oven for 6 h to obtain vinyl-modified mesoporous silica. A2: All the vinyl-modified mesoporous silica obtained in A1 was added to 2000 parts xylene, followed by 300 parts dodecyl methacrylate and 6 parts azobisisobutyronitrile. The mixture was ultrasonically dispersed at 500W for 25 min, then heated to 75℃ under nitrogen protection and stirred at a constant temperature for 12 h. After the reaction was completed, 6000 parts petroleum ether was added to the system, and the mixture was allowed to stand for 6 h to allow the solid to fully separate. The solid was then collected by centrifugation at 5000 rpm for 20 min to obtain grafted mesoporous silica. A3: All the grafted mesoporous silica obtained in A2 was added to 1200 parts of isopropanol, followed by 80 parts of epichlorohydrin and 15 parts of triethylamine. The mixture was heated to 60℃ and stirred at a constant temperature for 7 hours. After the reaction was completed, the solid was collected by centrifugation at 5500 rpm for 25 minutes. The solid was washed twice with a 5% sodium bicarbonate solution and then three times with deionized water. It was then dried at 70℃ for 4 hours and then heated to 85℃ for 3 hours to obtain modified mesoporous silica. B1: Take 20 parts of bamboo charcoal, crush it, and pass it through a 300-mesh sieve. Add 170 parts of a 12% potassium hydroxide solution and stir to activate it at 85℃ for 5 hours. After activation, cool it to room temperature, filter to collect the solid, wash it with deionized water until neutral, and dry it in a 115℃ drying oven for 6 hours. Place the dried solid in a tube furnace, purge it with nitrogen for protection, heat it to 820℃ at a rate of 6℃ / min, hold it at that temperature for 2.5 hours, and then cool it naturally to room temperature to obtain highly active bamboo charcoal powder. B2: Add all the highly active bamboo charcoal powder obtained in B1 to 100 parts of a 6% (w / w) potassium permanganate solution and stir at 35°C for 3.5 h. After the reaction is complete, add 50 parts of a 0.12 mol / L hydrochloric acid solution to the system and continue stirring for 45 min. Then filter to collect the solid, wash with deionized water until neutral, place in a vacuum drying oven, and dry at 65°C and -0.1 MPa for 4.5 h to obtain oxidized bamboo charcoal powder. B3: All the oxidized bamboo charcoal powder obtained in B2 was added to 90 parts by mass of 9% polyethyleneimine aqueous solution (polyethyleneimine molecular weight 30,000), and ultrasonically dispersed at 320W for 18 min. Then, 11 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide were added, and the mixture was stirred at 38℃ for 6.5 h. After the reaction was completed, the solid was collected by centrifugation at 4200 rpm for 18 min, washed 4 times with deionized water, and then washed 2 times with anhydrous ethanol. The solid was then placed in a vacuum drying oven and dried at 75℃ for 5.5 h to obtain modified bamboo charcoal powder.

[0033] S1: Lavender essential oil and anhydrous ethanol were mixed at a mass ratio of 1:3.7. The lavender essential oil was added to the anhydrous ethanol and stirred until homogeneous to obtain a lavender essential oil ethanol solution. The modified mesoporous silica obtained in A3 was added to this solution, with a mass ratio of modified mesoporous silica to lavender essential oil ethanol solution of 1:9.5. The mixture was ultrasonically dispersed at 500W for 50 min, and then allowed to stand at 32℃ for 7 h. After standing, the solid was collected by centrifugation at 9000 rpm for 15 min to obtain the essential oil-mesoporous complex. S2: Add chitosan to a 1.2% acetic acid solution with a mass ratio of 1:50. Stir until the chitosan is completely dissolved. Add the modified bamboo charcoal powder obtained in B3 to the solution with a mass ratio of 1:5. Disperse the solution with ultrasonic power at 450W for 30 minutes to obtain a bamboo charcoal composite solution. S3: The essential oil-mesoporous complex obtained in S1 was added to the bamboo charcoal composite solution obtained in S2, with a mass ratio of essential oil-mesoporous complex to bamboo charcoal composite solution of 1:11.5. The mixture was stirred and dispersed at 450 rpm for 35 min to obtain a suspension. A 2.5% (w / w) glutaraldehyde aqueous solution was added to the suspension, with a mass ratio of suspension to glutaraldehyde aqueous solution of 1:4.8. After all the solution was added, the temperature was raised to 45℃, and the mixture was stirred at a constant temperature of 300 rpm for 2.5 h. After the reaction was completed, the solid was collected by filtration, washed four times with deionized water, and then dried in a vacuum drying oven at 80℃ for 7 h to obtain lavender essential oil sustained-release capsules for air purification.

[0034] Comparative Example 1 Compared with Example 2, this comparative example replaces the "modified mesoporous silica prepared in steps A1-A3" with an equal mass of "unmodified mesoporous silica". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0035] Comparative Example 2 Compared with Example 2, this comparative example replaces "modified mesoporous silica prepared in steps A1-A3" with an equal mass of "mesoporous silica modified only by vinyl in A1 (omitting hydrophobic grafting in A2 and epoxy introduction in A3)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0036] Comparative Example 3 Compared with Example 2, this comparative example replaces "modified mesoporous silica prepared in steps A1-A3" with an equal mass of "grafted mesoporous silica prepared in steps A1-A2 (epoxy introduction step in A3 is omitted)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0037] Comparative Example 4 Compared with Example 2, this comparative example replaces the "modified bamboo charcoal powder prepared in steps B1-B3" with an equal mass of "unmodified bamboo charcoal that has only been pulverized through a 250-mesh sieve". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0038] Comparative Example 5 Compared with Example 2, this comparative example replaces "modified bamboo charcoal powder prepared in steps B1-B3" with an equal mass of "modified bamboo charcoal powder prepared in steps B2-B3 (steps in B1 omitted)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0039] Comparative Example 6 Compared with Example 2, this comparative example replaces "modified bamboo charcoal powder prepared in steps B1-B3" with an equal mass of "modified bamboo charcoal powder prepared in B1 and B3 (step B2 omitted)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0040] Comparative Example 7 Compared with Example 2, this comparative example replaces "modified bamboo charcoal powder prepared in steps B1-B3" with an equal mass of "oxidized bamboo charcoal powder prepared in steps B1-B2 (step B3 omitted)". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0041] Comparative Example 8 Compared with Example 2, this comparative example replaces "polyethyleneimine (polyethyleneimine, molecular weight 30,000) in step B3" with an equal mass of "γ-aminopropyltriethoxysilane". All other steps and parameters are the same, and will not be repeated in this comparative example. Finally, lavender essential oil sustained-release capsules for air purification are obtained.

[0042] The performance of the lavender essential oil sustained-release capsules for air purification prepared in Examples 1-3 and the lavender essential oil sustained-release capsules for air purification prepared in Comparative Examples 1-8 were tested, and the results are recorded in Table 1.

[0043] 1. Essential oil leakage rate detection: Standard curve plotting: Prepare 0.1-1.0 mg / mL lavender essential oil ethanol standard solution, and use a gas chromatograph (Agilent 7890A, FFAP column, column temperature program set to initial temperature 60℃, then increase the temperature at a rate of 10℃ / min until the temperature reaches 180℃ and is maintained) to measure the peak area and establish a concentration-peak area standard curve. Sample testing: Weigh 0.5g of sample, add 20mL of anhydrous ethanol and ultrasonically extract for 30min (300W power), centrifuge at 12000rpm for 15min, take the supernatant and filter through a 0.22μm filter membrane, measure the peak area by gas chromatography, substitute into the standard curve to calculate the essential oil content, and obtain the total amount of essential oil encapsulated in microcapsules; take 5.0g of sample and spread it evenly on a petri dish, store it in a 60℃ forced-air drying oven (forced air rate 1m / s) for 5 days, and measure the essential oil content after storage according to the above method to obtain the essential oil content after storage.

[0044] formula: .

[0045] 2. Air purification test: Testing procedure: Formaldehyde (concentration 1.0 mg / m³) is introduced into a sealed chamber (volume 1 m³, temperature 25℃, RH 50%). 3 Add 5g of sample, turn on a 300W xenon lamp (simulating natural light, light intensity 10000 lux), and take samples at 12h, 24h, and 48h respectively; measure the residual concentration using a gas chromatograph (Agilent 7890A, FFAP column) and calculate the degradation rate.

[0046] formula: .

[0047] The test results are shown in Table 1: Table 1: Performance testing parameters for lavender essential oil sustained-release capsules According to the data in Table 1, the lavender essential oil sustained-release capsules for air purification prepared by this invention have excellent essential oil encapsulation stability and efficient formaldehyde purification ability. They can not only effectively reduce leakage during essential oil storage, but also continuously and efficiently degrade formaldehyde in the air. This is due to its composite carrier structure of "modified mesoporous silica-modified bamboo charcoal powder-chitosan", as well as the complete process design of three-step modification of mesoporous silica (A1-A3) and three-step modification of bamboo charcoal powder (B1-B3). The synergistic effect of each modification step and component ensures the core performance of the product.

[0048] A comparison of Example 2 and Comparative Example 1 shows that the complete mesoporous silica modification process (vinyl modification in A1, hydrophobic grafting in A2, and epoxy introduction in A3) is crucial for improving product performance. Unmodified mesoporous silica lacks the ability to hydrophobically lock in essential oils and the cross-linking activity with other components. It cannot effectively encapsulate essential oils and is difficult to form a stable composite carrier structure, leading to a significant increase in essential oil leakage and a substantial decrease in formaldehyde purification efficiency. This fully demonstrates that multi-step modification of mesoporous silica is fundamental to ensuring the stability of essential oil encapsulation and the efficiency of formaldehyde purification in the product.

[0049] A comparison of Example 2 and Comparative Example 2 shows that the modification of mesoporous silica requires the synergistic completion of three steps: A1, A2, and A3. The A1 step alone involves vinyl modification, lacking the hydrophobic grafting of step A2 and the epoxy introduction of step A3. This prevents the formation of an effective hydrophobic layer on the mesoporous surface to lock in the essential oils, and also fails to provide crosslinking sites for the reaction with the modified bamboo charcoal powder. Consequently, the mesoporous silica's ability to encapsulate the essential oils and its synergistic effect with the carrier are weakened. The final product exhibits a higher essential oil leakage rate and a lower formaldehyde degradation efficiency than Example 2. This demonstrates that steps A2 and A3 play an irreplaceable role in optimizing the performance of mesoporous silica and enhancing its synergistic effect with the carrier.

[0050] A comparison of Example 2 and Comparative Example 3 shows that the introduction of epoxy in step A3 is crucial for the formation of a stable cross-linked network between mesoporous silica and modified bamboo charcoal powder. With only vinyl modification in A1 and hydrophobic grafting in A2 completed, the epoxy groups introduced in step A3 are missing. Consequently, the mesoporous silica cannot cross-link with the amino groups on the surface of the modified bamboo charcoal powder, weakening the bonding force between the carriers and making it difficult to form a tight composite structure. This not only leads to easy leakage of essential oils from the carrier gaps but also reduces the adsorption and degradation effect on formaldehyde, resulting in product performance inferior to Example 2. This highlights the important significance of step A3 in the synergistic effect of carrier network stability and performance.

[0051] A comparison of Example 2 and Comparative Example 4 shows that the complete modification process of bamboo charcoal powder (activation in B1, oxidation in B2, and polyethyleneimine grafting in B3) is the core to improving the formaldehyde purification capacity and essential oil encapsulation stability of the product. Unmodified bamboo charcoal powder has small pore size, limited specific surface area, and lacks active groups on its surface. It cannot provide sufficient formaldehyde adsorption sites, nor can it form a synergistic effect with mesoporous silica and chitosan, resulting in a significant reduction in formaldehyde degradation rate. At the same time, the looseness of the carrier structure also increases the risk of essential oil leakage, fully demonstrating the key functional value of modified bamboo charcoal powder in the product.

[0052] A comparison of Example 2 and Comparative Example 5 shows that the bamboo charcoal activation treatment in step B1 plays a decisive role in improving the adsorption capacity of bamboo charcoal powder. By omitting the potassium hydroxide activation and high-temperature insulation in step B1, the pore size of the bamboo charcoal powder cannot be effectively expanded, and the specific surface area is difficult to increase. Even after subsequent oxidation and polyethyleneimine grafting, the number of formaldehyde adsorption sites provided is still far fewer than that of activated bamboo charcoal powder, resulting in a significantly lower formaldehyde degradation rate than in Example 2. This demonstrates that step B1, by regulating the microstructure of bamboo charcoal, lays the foundation for subsequent performance optimization.

[0053] A comparison of Example 2 and Comparative Example 6 shows that the potassium permanganate oxidation treatment in step B2 is a crucial step in enhancing the chemical activity of bamboo charcoal powder. Omitting step B2 prevents the introduction of sufficient carboxyl and hydroxyl groups onto the surface of the bamboo charcoal powder, weakening its chemical adsorption capacity for formaldehyde and reducing the grafting efficiency of polyethyleneimine in the subsequent step B3. This results in decreased reactivity of the bamboo charcoal powder with formaldehyde and its binding capacity with other carriers, ultimately leading to a lower formaldehyde degradation rate than in Example 2. This highlights the necessity of step B2 in modifying the chemical properties of bamboo charcoal powder.

[0054] A comparison of Example 2 and Comparative Example 7 shows that the polyethyleneimine grafting treatment in step B3 is crucial for enhancing the formaldehyde degradation capacity of bamboo charcoal powder and the cross-linking effect of the carrier. Omitting step B3 results in the lack of amino groups introduced by polyethyleneimine on the surface of the bamboo charcoal powder. This prevents the formaldehyde from being fixed and degraded through chemical reactions with the amino groups, and also hinders the formation of stable cross-links with the epoxy groups of mesoporous silica, leading to a decrease in the formaldehyde degradation rate. Simultaneously, the weakened stability of the carrier structure also affects the encapsulation of essential oils. This demonstrates that step B3 is key to achieving the dual functions of "adsorption-reaction" and synergistic effects between the bamboo charcoal powder and the carrier.

[0055] A comparison of Example 2 and Comparative Example 8 shows that using polyethyleneimine (PEI) with a molecular weight of 30,000 as a grafting agent for bamboo charcoal powder is more advantageous than γ-aminopropyltriethoxysilane. The long-chain structure of polyethyleneimine provides more amino sites, allowing it to react fully with formaldehyde and form a tighter cross-linking network with the epoxy groups of mesoporous silica. In contrast, the replaced silane grafting agent has limited amino content and weaker cross-linking effect, resulting in lower formaldehyde degradation rate and less stable essential oil encapsulation compared to Example 2. This demonstrates that polyethyleneimine is a suitable grafting agent for ensuring the synergistic effect of bamboo charcoal powder function and carrier.

[0056] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing lavender essential oil sustained-release capsules for air purification, characterized in that, The preparation steps include the following: S1: Add lavender essential oil to anhydrous ethanol to obtain a lavender essential oil ethanol solution. Add modified mesoporous silica to the lavender essential oil ethanol solution and disperse it by ultrasonication. Let it stand and separate by centrifugation to obtain an essential oil-mesoporous complex. S2: Add chitosan to acetic acid solution and stir evenly, add modified bamboo charcoal powder, and ultrasonically disperse to obtain bamboo charcoal composite solution; S3: Add the essential oil-mesoporous complex to the bamboo charcoal composite solution, stir and disperse to obtain a suspension, add a cross-linking agent solution to the suspension, heat and stir, after the heating and stirring is completed, filter, wash and dry to obtain lavender essential oil sustained-release capsules for air purification.

2. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 1, characterized in that, In step S1, the modified mesoporous silica is prepared by the following method: A1: Mesoporous silica was added to toluene, vinyltrimethoxysilane was added, the pH was adjusted, and the reaction was stirred under reflux under nitrogen protection. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain vinyl-modified mesoporous silica. A2: Vinyl-modified mesoporous silica was added to xylene, followed by dodecyl methacrylate and azobisisobutyronitrile. After ultrasonic dispersion, the mixture was heated and stirred under nitrogen protection. After the reaction was completed, petroleum ether was added, the mixture was allowed to stand, and then centrifuged to obtain grafted mesoporous silica. A3: Grafted mesoporous silica was added to isopropanol, followed by epichlorohydrin and triethylamine. The mixture was heated and stirred to react. After the reaction was completed, the silica was centrifuged, washed, and dried to obtain modified mesoporous silica.

3. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 2, characterized in that, The modified mesoporous silica raw materials, by weight, include: 70-100 parts mesoporous silica, 800-1200 parts toluene, 15-25 parts vinyltrimethoxysilane, 1500-2000 parts xylene, 200-300 parts dodecyl methacrylate, 3-6 parts azobisisobutyronitrile, 800-1200 parts isopropanol, 50-80 parts epichlorohydrin, and 10-15 parts triethylamine.

4. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 1, characterized in that, The modified bamboo charcoal powder is prepared by the following method: B1: Take bamboo charcoal powder, sieve it, add potassium hydroxide solution, stir and activate it, cool it, filter it and dry it; then heat it and keep it warm under a nitrogen atmosphere, and after natural cooling, obtain highly active bamboo charcoal powder. B2: Add highly active bamboo charcoal powder to potassium permanganate solution and stir to react. Add hydrochloric acid solution and continue stirring. Filter and dry to obtain oxidized bamboo charcoal powder. B3: Add oxidized bamboo charcoal powder to an aqueous solution of polyethyleneimine and disperse it by ultrasonication. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide and stir to react. After the reaction, centrifuge, wash and dry to obtain modified bamboo charcoal powder.

5. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 4, characterized in that, The raw materials for the modified bamboo charcoal powder, by weight, include: 12-20 parts bamboo charcoal, 110-170 parts potassium hydroxide solution, 80-100 parts potassium permanganate solution, 30-50 parts hydrochloric acid solution, 70-90 parts polyethyleneimine aqueous solution, and 8-11 parts 1-ethyl-(3-dimethylaminopropyl)carbodiimide.

6. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 5, characterized in that, The potassium hydroxide solution has a mass fraction of 8%-12%, the potassium permanganate solution has a mass fraction of 4%-6%, the hydrochloric acid solution has a mass concentration of 0.08mol / L-0.12mol / L, and the polyethyleneimine aqueous solution has a mass fraction of 7%-9%.

7. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 1, characterized in that, In step S1, the mass ratio of lavender essential oil to anhydrous ethanol is 1:2.3-3.7, and the mass ratio of modified mesoporous silica to lavender essential oil ethanol solution is 1:5.5-9.

5.

8. The method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 1, characterized in that, In step S2, the mass ratio of chitosan to acetic acid solution is 1:40-50, and the mass ratio of modified bamboo charcoal powder to chitosan is 1:4-1:

5.

9. A method for preparing a lavender essential oil sustained-release capsule for air purification according to claim 1, characterized in that, In step S3, the mass ratio of essential oil-mesoporous complex to bamboo charcoal composite solution is 1:8.5-11.5; the crosslinking agent solution is glutaraldehyde aqueous solution, and the mass ratio of suspension to crosslinking agent solution is 1:3.8-4.8; the temperature for heating and stirring is 40℃-45℃, the rotation speed is 250rpm-300rpm, and the time is 2h-2.5h.

10. A lavender essential oil sustained-release capsule for air purification prepared by a method according to any one of claims 1-9.

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